Prepare the environment
Assign an onboarding owner. Prepare access to repositories, development environments and approved communication tools. Use least-privilege permissions and document how access will be reviewed and removed.
Give context before tickets
Explain the users, the product constraints and the decisions behind the current architecture. A short conversation with a product owner and a guided code walkthrough often uncover more useful context than an unstructured document archive.
Choose a meaningful first task
Pick a bounded change that exercises the normal development, review and release process. Schedule a check-in to discuss friction. The objective is to understand the workflow and establish a reliable feedback loop, not to judge speed on day one.